Needle-less injector and method of fluid delivery

ABSTRACT

A needle-less injector device for delivering a dose of fluid intradermally, subcutaneously or intramuscularly to an animal or human. The device includes an inner housing having opposed ends. A syringe is disposed in one end of the inner housing. The syringe includes a nozzle for delivering a dose of fluid held within the syringe. A plunger is movably disposed within the syringe. A spring powered hammer is movably disposed within the inner housing. The hammer cooperates with the plunger to drive the dose of medicament from the nozzle. An injection delivery spring for powering the hammer is positioned and compressed between the other end of the inner housing and the spring powered hammer. An outer housing slideably supports the inner housing. A skin tensioning spring is mounted between the inner housing and the outer housing, the skin tensioning spring biasing the nozzle of the syringe against the animal or human. A trigger mechanism is disposed in the outer housing, the trigger mechanism cooperating with the spring powered hammer to release the injection delivery spring, wherein the size of the injection delivery spring and the length of the hammer dictate the amount of dose delivered and whether the dose is delivered intradermally, subcutaneously or intramuscularly to an animal or human.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. continuation of 12/575,394, entitled “Needle-Less Injector andMethod of Fluid Delivery,” filed on Oct. 7, 2009, which is acontinuation of U.S. patent application Ser. No. 11/598,193, entitled“Needle-less Injector and Method of Fluid Delivery,” filed on Nov. 13,2006, which is a continuation-in-part of U.S. patent application Ser.No. 11/121,439, entitled “Needle-less Injector,” filed May 3, 2005 andwhich is related to U.S. patent application Ser. No. 11/185,736,entitled “Needless Injector and Ampule System,” filed Jul. 21, 2005 andU.S. patent application Ser. No. 11/453,248, entitled “Vial System andMethod for a Needle-less Injector,” filed Jun. 15, 2006, each of whichis hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a needle-less injector that can delivera high-pressure jet of fluid, such as a medicament, intramuscularly,intradermally and/or subcutaneously into the tissue a human or animal,and more particularly to a method of delivering a specific dose ofmedicament via a needle-less injector.

2. Description of Related Art

The advantages of needle-less injection devices have been recognized forsome time. Some of these advantages include: the absence of needle stickinjuries that present hazards to healthcare workers; a reduction in therisk of cross-contamination among patients, whether, human or animal;the elimination of needle breakage in the tissue of the human or animal;and that the jet of liquid medicament is generally smaller than thediameter of a hypodermic needle and thus may be less invasive than ahypodermic needle.

Because of the well-known advantages of needle-less injection, there aremany different kinds of such devices, including pneumatic needle-lessinjection devices that are designed to provide multiple doses topatients or animals, or gas actuated, which are for single or multipleuse. Most known needle-less injection devices operate by using a pistonto drive the fluid to be delivered though a fine nozzle that creates asmall, high pressure stream that penetrates the skin simply due to thehigh pressure. Multi-dose and single-dose devices depend on a source ofenergy to drive air or working fluid that is used to operate the pistonthat drives the fluid through the nozzle. Thus, a serious limitation ofthese devices is that they must have a readily available source ofenergy to drive the piston. This makes these devices impractical for usein hospitals and/or clinics, and in most field situations, especially inremote areas where access to dependable energy is uncertain.

These injector devices are also large, sometimes expensive units, andgenerally adapted to retain large quantities of medicament for repeatedinjections. Most of these machines are not portable and havehistorically been used chiefly for mass inoculation programs.

Because of the disadvantages of injection devices that use high-pressurefluids to drive the piston and deliver multiple injections, a great dealof attention has been given to the development of a spring-poweredneedle-less injection device for delivering a single injection. Thesuccess of the known devices has been limited, due to problemsassociated with safety and reliability. The issues regarding safetygenerally involve the possibility of accidental discharge of the deviceand the possibility of transmitting diseases between patients due tocarryover of body fluids. The problems associated with reliabilitygenerally involve the device's ability to deliver a full, known dose ofthe liquid.

Safety issues generally arise in association with devices that haveexposed triggers or include a hammer or piston driving device that canextend beyond the inner housing of the injector. The risk of using thistype of device is similar to the risks associated with the triggers onfirearms, and that is the inadvertent pressing of the trigger, canresult in the accidental or premature firing of the device.

Reliability issues include a broad spectrum of problems. One significantproblem is the creation of a suitable jet or stream of fluid and theintroduction of this jet on to the skin of the animal or human.Preferably, the jet will be a very fine jet that will impact a sectionof taut skin at an angle of incidence of preferably 90 degrees. Most ofthe energy of the stream is used to penetrate the skin when the jetimpacts at approximately 90 degrees to the skin. Additionally, bykeeping the skin taut prior to delivering the jet of fluid, the skin isnot allowed to flex, and thus more of the energy from the jet is used topenetrate the skin rather than deflecting or moving the skin.

Yet another problem associated with needle-less devices is maintenanceof a required amount of pressure during the delivery of the medicamentfrom the reservoir, through the nozzle. As disclosed in U.S. Pat. No.6,942,638, the entirety of which is hereby incorporated by reference, aloss of pressure can affect the amount of medicament delivered.

There are also disadvantages related to the containment of the fluidformulations in single dose needle-less injectors. Individual doses of aliquid formulation can be delivered via the injector. However, often thevolume of medicament held in the conventional injectors is too large,for example, when injecting an infant or small animal, such as a mouse.Often one-half or more of the dosage is not required and hence would bewasted or the injection could not be given safely to such patient. Thisdecreases the practicality and use of the injectors in certainenvironments.

Another problem with medicament containment is that many materialsproposed for the vials are unsuitable for long-term contact with themedicament, or at least would require extensive and costly validationfor each application.

Another disadvantage of known needle-less injectors is the inability todirect the location of the injection, i.e., intramuscularly,intradermally and/or subcutaneously.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided ahand-held, spring-powered, needle-less injector device that can delivera single dose of liquid, such as a medicament, both safely and reliablywithout an external power source.

In another aspect, the needle-less injector of the present inventprevents accidental discharge. The needle-less injector device has atrigger stop that prevents operation of the trigger when the innerhousing in not in the firing position. An example of this trigger stopincludes a protrusion that extends from the outer housing and impedesthe movement of the trigger when inner housing is not in the firingposition. The protrusion then moves away from the trigger when the innerhousing is moved into the firing position.

In yet another aspect, the needle-less injector device of the presentinvention uses a single-use, disposable needle free syringe containing aliquid for delivery. The syringe includes a connector at one end and anozzle and skin tensioner at the other end. The connector can be abayonet type connector. The skin tensioner can be a ridge that surroundsthe nozzle. The syringe is easily insertable into the injector andprovides for a safer healthcare environment.

It is still another aspect of the present invention to provide aneedless injector that can deliver smaller doses of medicament withoutproviding different vial sizes.

Another aspect of the present invention is to provide a needlessinjector that can control the particular location of the injection,i.e., intramuscularly, intradermally and/or subcutaneously.

During operation of the injector, the user will position the hammer atthe cocked position and insert the syringe into the leading end of theinner housing. The syringe can be pre-filled with the liquid that is tobe delivered to the animal or human as described above. The user pressesthe nozzle and skin tensioner against the animal or human, causing theinner housing of the device to move against the skin tensioning spring,into or relative to the outer housing to the firing position. Once theinner housing is moved to the firing position, the pressure of the skintensioning spring is reacted against the animal or human, causing theskin to be stretched taut across the skin tensioner. This stretching ofthe skin across the skin tensioner will position the target area of theskin at a right angle to the syringe and the nozzle. The movement of theinner housing to the firing position also results in the movement of aprotrusion relative to the inner housing such that the protrusion nolonger obstructs the movement of the trigger. The user then simplypresses the trigger, which releases the spring driven hammer, which inturn drives the fluid through the nozzle of the syringe and into theanimal or human's skin.

The hammer may drive a separate plunger with a seal through the syringeto expel the fluid in the syringe through the nozzle of the syringe.However, the syringe may incorporate portions, or all, of the plunger todeliver different amounts of medicament into the skin.

Still further, it is contemplated that the use of a separate plungerwill allow the use of a mechanical cocking device that will push againstthe hammer to move the hammer from an unloaded position to the cockedposition.

According to these and other aspects there is provided a needle-lessinjector device for delivering a dose of fluid intradermally,subcutaneously or intramuscularly to an animal or human. The deviceincludes an inner housing having opposed ends. A syringe is disposed inone end of the inner housing. The syringe includes a nozzle fordelivering a dose of fluid held within the syringe. A plunger is movablydisposed within the syringe. A spring powered hammer is movably disposedwithin the inner housing. The hammer cooperates with the plunger todrive the dose of medicament from the nozzle. An injection deliveryspring for powering the hammer is positioned and compressed between theother end of the inner housing and the spring powered hammer. An outerhousing slideably supports the inner housing. A skin tensioning springis mounted between the inner housing and the outer housing, the skintensioning spring biasing the nozzle of the syringe against the animalor human. A trigger mechanism is disposed in the outer housing, thetrigger mechanism cooperating with the spring powered hammer to releasethe injection delivery spring, wherein the size of the injectiondelivery spring, skin tensioning spring and the length of the hammerdictate the amount of dose delivered and whether the dose is deliveredintradermally, subcutaneously or intramuscularly to an animal or human.

According to these and other aspects there is provided a method fordelivering a dose of medicament intradermally, subcutaneously orintramuscularly to an animal or human. The method includes the steps ofproviding a syringe containing a predetermined dose of medicament, thesyringe including a nozzle for delivering the medicament and a skintensioner, and providing a needle-less injector device. The needle-lessinjector device includes an inner housing having a leading end and atrailing end, the leading end of the inner housing being adapted forreceiving the syringe; a hammer movably disposed within the innerhousing; an injection delivery spring disposed in the inner housingbetween the hammer and the trailing end of the inner housing for drivingthe hammer; a plunger movably and sealingly located within the syringe,the plunger being driven by the hammer; a hollow outer housing adaptedfor slideably receiving the inner housing therein, the inner housingbeing movable within the hollow outer housing between a safe positionand a firing position; and a skin tensioning spring mounted between theinner housing and the outer housing, the skin tensioning spring biasingthe nozzle toward the skin of the human or animal. When the nozzle ofthe syringe is placed against the skin, and the trigger is pressed, thehammer is released and the hammer forces the plunger through the syringeto eject the fluid from the syringe through the nozzle into the skin,wherein the size of the injection delivery spring, skin tensioningspring and the length of the hammer dictate the amount of dose deliveredand whether the dose is delivered intradermally, subcutaneously orintramuscularly to an animal or human.

These and other objects, features, aspects, and advantages of thepresent invention will become more apparent from the following detaileddescription of the preferred embodiment relative to the accompanieddrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cutaway of the needless injector device of thepresent invention.

FIG. 2 is a top view of the device of FIG. 1.

FIG. 3 is an exploded view of the needless injector device of thepresent invention.

FIG. 4 is a cross-sectional view of the needless injector device shownin the ready position, prior to moving the inner housing into the firingposition.

FIGS. 5-7 are a cross-sectional view of the needless injector device ofthe present invention in the sequential firing positions.

FIG. 8 is a cross-sectional view of the needless injector device of thepresent invention in a post-injection position.

FIG. 9A is a perspective view of an embodiment of the syringe and sealof the present invention.

FIG. 9B is a top view of the syringe and seal of FIG. 9A.

FIG. 10 is a perspective view of a carrying and cocking device for theneedle-less injection device of the present invention.

FIG. 11 is a side view of the carrying and cocking device of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1-5, a hand-held, spring-powered, needle-lessinjector device 10 includes an inner housing 12 having a leading end 14and a trailing end 16. The leading end 14 of the inner housing 12 isconstructed and arranged to receive a vial, ampule or syringe 18 that isused to hold a fluid 20 that is to be delivered through the skin 22covering tissue of an animal or human 24 and into the tissue thereof. Itshould be appreciated that although the present invention is describedin relation to “skin” and “animal,” it is intended to include humans,animals and other surfaces. As will be described further herein, theneedle-less injector of the present invention is designed to deliver themedicament intramuscularly, intradermally or subcutaneously to the humanor animal. An intramuscular injection is one that passes through theskin and subcutaneous tissue and penetrates the underlying skeletalmuscle. A subcutaneous injection is one that fully penetrates the skinand is retained in the space between the skin and the underlyingmusculature. An intradermal injection floods the epidermal and dermallayers with fluid but does not travel as deep as a subcutaneousinjection. There are many reasons why drug delivery to a particularlocation is important, for example, speed of absorption, decreasedside-effects, decreased pain, etc. Moreover, some vaccines areformulated to be delivered to the intramuscular area of the body, someare formulated for subcutaneous and others can be administered to bothareas and others are targeted to the dentritic cells of the skin.

As shown in FIGS. 1-3, inner housing 12 is movably mounted within anouter housing 28 so as to slide along the axial direction thereof. Theinner housing is movable from a ready position, illustrated in FIG. 4,to a firing position, sequentially illustrated in FIGS. 5-7.

Inner housing 12 can be moved into the ready position of FIG. 4 by askin tensioning spring 30 that is mounted between the inner housing 12and the outer housing 28. The skin tensioning spring 30 has numerousfunctions. One function of spring 30 is to cooperate with the structureof the syringe 18 to pull the animal's skin 22 taut while positioningthe skin 22 prior to delivering the fluid 20 into the animal or humantissue 24. Another function of the skin tensioning spring 30 is tocooperate with a trigger mechanism 32 to ensure that the device 10cannot be fired until the device 10 is properly positioned against theskin 22 covering the tissue of the animal or human 24, and the properamount of pressure or force exists between the syringe 18 and the skin22.

The amount of force required to be applied against the skin variesdepending on the physical characteristics of the patient or animal beinginjected with the device 10, as well as the location of the delivery.For example, a mature adult may require higher force to hold the skintaut and penetrate the skin as compared to a child or infant, simply dueto the effects of aging on the elasticity of the skin. Likewise, in ananimal, it can be more difficult to inject the tougher skin surroundingthe back or neck. Accordingly, it is contemplated that the disclosedinvention can be manufactured with different skin-tensioning springs,each skin tensioning spring being of a stiffness that is appropriate fora particular application. It is further contemplated that the forceimposed by the skin tensioning spring may be made adjustable, forexample by adding a threaded plug that screws against the spring to addpre-tension.

The amount of pressure or force that is used to hold syringe 18 againstskin 22 is an important variable in the injection process. Needle-lessinjection devices are capable of delivering fluids through the skin 22of the animal or human 24 by injecting a jet of fluid 34 into the skin22 at a sufficiently high pressure and velocity so that fluid jet 34penetrates through the skin 22 and into the tissue of the animal orhuman 24.

Important factors that contribute to the device's ability to accomplishthe task of forming a jet of fluid 34 are the amount of energy that canbe quickly and efficiently transferred to the fluid jet 34, and thedevice's ability to position the fluid jet 34 such that the energy ofthe jet is efficiently used to penetrate the tissue.

The energy to be transferred to fluid 20 is stored in an injectiondelivery spring 36 that drives a plunger and seal 38 into the syringe 18in order to force the fluid 20 through a nozzle 40 (FIG. 1) that formsthe jet of fluid 34, as will be described more fully herein. Injectiondelivery spring 36 is positioned between a head 50 (FIG. 3) of a hammer44 and the trailing end 16 of inner housing 12.

In order to obtain the most efficient delivery of the jet of fluid 34into the skin 22 the nozzle 40 should be positioned at a right anglerelative to the skin 22 as the jet of fluid 34 is delivered. Althoughthe device may still operate at other angles, delivering the jet offluid 34 at some angle other than a right angle could result in acomponent of the force with which the jet of fluid strikes the skincould be parallel to the skin rather than into the skin 22.

The stiffness of the skin-tensioning spring 30 is selected such that theappropriate amount of force is imposed against the skin 22 of the animalor human 24. The stiffness of the skin-tensioning spring 30 iscalculated from the well-known formula:

F=k*x,

where F is the required force at the firing position, x is the distanceof travel (FIG. 4) of the inner housing 12 relative to the outer housing28 to position the device in the firing position (where the protrusion46 does not impede movement of the trigger mechanism 32), and k is thespring constant of the skin-tension spring 30.

Although, the present invention is described in particular topositioning the device directly against the skin, it should beappreciated that the above parameters can be chosen to deliver the jetof fluid through the fabric of a patient. For example, in the case of apandemic outbreak or a terrorist attack, the medicament can be delivereddirectly to the patient without the need to remove potentiallyprotective clothing. Also, in the application of a resuscitation agent,the device of the present invention could be used by emergency medicalpersonnel to quickly deliver the resuscitation agent directly throughthe patient's clothing without the need to take the potentially lifethreatening time to expose the patient's skin.

For delivery through the skin surface, syringe 18 can include a skintensioner 42 that surrounds nozzle 40. Skin tensioner 42 can be a discpositioned approximately about the nozzle exit. It should be appreciatedthat skin tensioner 42 can take other shapes.

As shown in FIGS. 3 and 9B, an installation ring 41 can be provided onsyringe 18. The installation ring 41 aids the user in the insertion ofsyringe 18 into the device 10 and in positioning the device 10 at aright angle to the skin as the jet of fluid 34 is to be delivered. Theskin tensioner 42 may cooperate with the installation ring 41 to pullthe skin taut as the device is pressed against the skin prior todelivery of the fluid jet 34. It should be appreciated that a certainminimum amount of force must be applied against the skin in order toensure that the skin is drawn tight prior to the release of the jet offluid 34.

Referring to FIGS. 1-8, injection delivery spring 36 has opposed ends.One end of spring 36 abuts against the trailing end 16 of the innerhousing. The other end of spring 36 abuts against head 50 of hammer 44.Hammer 44 in turn abuts against plunger and seal 38. It should beappreciated that hammer 44 and plunger 38, although illustrated as twoseparate pieces, can also be formed of a single piece.

Plunger 38 is movably and sealingly disposed in syringe 18. Thus, whileplunger 38 can move within the syringe it is sealingly engaged with aninner diameter of the syringe such that the dose of medicament cannotleak therefrom. As shown in FIG. 3, the spring powered hammer 44 rideswithin a sleeve 47 that includes a slot 49 for accepting latchingcomponents of the trigger mechanism 32.

Outer housing 28 includes an aperture 56. A trigger mechanism 32 ismounted in inner housing 12 and protrudes through aperture 56 so as tobe engageable by a user. Trigger mechanism 32 includes a trigger 45 anda link 58 that controls the release of hammer 44. As can be understoodfrom comparing the sequential illustrations of FIGS. 4-8, the firing ofthe device 10 to deliver a dose of fluid is accomplished by pressing thetrigger 45 in the direction of arrow 48 after the device 10 is in thefiring position, illustrated in FIG. 5. However, the trigger 45 of thetrigger mechanism 32 can only release the plunger and seal 38 when thedevice 10 is in the firing position, illustrated in FIG. 5. When thedevice 10 is in another position (other than the firing position), suchas the ready position of FIG. 4, the trigger link 58 of mechanism 32cannot be pressed to release the hammer 44. The release of the hammer 44is prevented for safety and for efficacy of the injection.

The unwanted activation of the trigger mechanism 32 is accomplished bypositioning a protrusion 46 below trigger 45. The protrusion 46 preventsmovement of the trigger 45 in the direction of arrow 48, preventing therelease of hammer 44, and thus preventing the firing of the device 10.According to a preferred embodiment of the invention the protrusion 46extends from the outer housing 28 to a location under the trigger 45.The protrusion 46 is positioned such that it interferes with themovement of the trigger 45 until the device 10 is in the firingpositions, as illustrated in FIG. 5-7. After firing, the trigger 45 willbe returned to its original position (FIG. 8).

In the preferred example of the invention, the movement of the innerhousing 12 relative to the outer housing 28 moves the position of thetrigger 45 (which is mounted from the inner housing 12) relative to theouter housing 28, which holds the protrusion 46. The amount of movementof the outer housing 28 relative to the inner housing 12 is accomplishedagainst the force of the skin-tensioning spring 30.

As shown in FIG. 6, once the inner housing 12 is positioned relative tothe outer housing 28 such that the desired amount of skin tensioningforce is applied to the skin 22 against the syringe 18, which alsopositions the device in the firing position, the pressing of the trigger45 causes the release of the spring powered hammer 44 from the cockedposition. When the trigger is released, injection delivery spring 36that has been manually compressed and latched to temporarily store theenergy until it is required fire the injector.

Referring to FIG. 7, when the trigger mechanism is pressed, spring 36 isreleased and hammer 44 is propelled against plunger 38 located in thesyringe, vial or ampule 18. The hammer drives plunger 38 against themedicament, producing a high pressured jet for injection purposes. Theplunger expels the medicament from a discharge orifice of nozzle 40 andinto the patient's skin, muscle and/or subcutaneous tissue.

The initial high pressure discharge causes the jet stream to pierce theskin with the initial injection of the medicament. After a short travel,the expansion of injection delivery spring 36 is completed and thecontinued movement of hammer 44 and the movement of plunger 38 into thesyringe is driven by tensioning spring 30 (FIG. 8). This movementcontinues the ejection of the jet of medicament from syringe 18 throughthe aperture in the skin created by the initial high intensity burst.Skin-tensioning spring can have a lower stiffness than the injectiondelivery spring.

Thus, the medicament can be delivered to a predetermined depth beneaththe surface, depending upon the magnitude of the pressure. After theminute opening in the skin has been produced, the pressure of the streamis immediately reduced to a lower second stage for completing transferof the remaining medicament from the syringe.

It is desirable that the needle-less injector of the present inventionhave adjustments for the delivered volume of the medicament. Injectiondelivery spring 36 can be chosen from a variety of spring weights toprovide different spring pressures and hence different delivery power ofthe medicament. As discussed above, the present invention is designed soas to offer different locations for the delivery of themedicament—intramuscularly, intradermally or subcutaneously to the humanor animal. A spring having a lighter weight will accommodate a smallerdose or a dose to a subject that has thinner skin, whereas a springhaving a larger weight can deliver a larger dose of medicament or a doseto a subject with thicker skin. As with the tensioning spring 30, aparticular delivery spring 36 can be chosen by the user and be deliveredin the packaged injector. Spring weights can range from 850 and above,more particularly, from 850 to 1980. However, spring weights vary insize and strength according to the tissues injected and it should beappreciated that a variety of springs are contemplated by the presentinvention and the disclosed range is only an example.

Syringe 18 includes the dose of medicament to be delivered. Depending onthe type of vaccine and the intended recipient, a particular dose ispredetermined by the manufacturer of the medicament or a physician.Typical vaccine dosages range of and about 0.1-1 cc.

However, recent clinical trials have proven that for some vaccines,reducing the amount of vaccine delivered still achieves the desiredlevel of efficacy as a larger dosage. Another manner in which theneedless-injector of the present invention can be used to provide custominjections is to deliver smaller doses of the medicament. In order toaccommodate different doses of medicament, the length of the hammer 44can be varied to accommodate a variety of volumes of doses. For example,a longer length hammer causes the plunger to extend further withinsyringe 18, decreasing the volume of medicament retained in the syringe18 prior to ejection from the vial 18. The firing of the injector willdispense a smaller amount of medicament in a shorter time than a shorterlength hammer, because the plunger will have less of a distance totravel within syringe 18. The present invention contemplates a deliveryrange of dose of and about 0.1 cc to 1 cc. However, it should beappreciated that other doses are contemplated by the present invention.

Thus, different doses can be accommodated by the present inventionwithout providing different sized syringes. By lengthening hammer 44,the dosage in syringe 18 can be reduced significantly, for example aslow as 0.1 cc. This provides a significant cost advantage. Importantly,lower doses also enable smaller animals and infants to be inoculated. Byadjusting the length of hammer 44 and providing a particular deliveryspring the amount of dosage and the location of delivery can allow for acustom injection. The length of the head of the hammer is increased inproportionately for the stroke. For example, for a 0.1 cc dose, thelength of the hammer is increased by ⅘ths of the stroke.

Syringe 18 can include a plurality circumferential stiffening ribs 52(FIGS. 9A-9B) that extend around a body 54 of syringe 18. Thesestiffening ribs help reduce the amount of deflection of the body 54 ofthe syringe 18 during the delivery of an injection.

As discussed above, disposable syringe 18 contains a dose of liquidformulation for delivery. Syringe 18 can be made of a readily injectionmoldable material, such as a pharmaceutical grade polypropylene or apolymer material. One example of such a polymer material is TOPAS®,manufactured by Ticona Engineering Polymers, a division of Celanese. Asdiscussed above, medical grade materials allow for factory pre-fillingwithout-interaction with the dose as opposed to filing on site justprior to injection.

Typically polypropylene is extremely difficult to engineer because ofpressure distortion. However, the design of the plunger, syringe and theresulting seal of the present invention overcomes previous manufacturingdifficulties.

Referring to FIGS. 10 and 11, it should be understood that the disclosedneedle-less injection device can be used with a combined cocking andcarrying device 60. The cocking and carrying device includes a cockinghammer 62 that is used to push the spring powered hammer 44 back to the“ready” position shown in FIG. 4. The cocking and carrying device 60also includes a cradle 64 that retains the outer housing 28 while thecocking hammer 62 is pushed against the spring powered hammer 44.

Cocking hammer 62, when pushed against spring powered hammer 44, movesthe hammer into the “ready” position illustrated in FIG. 4. It should beunderstood that the cocking and carrying device 60 will cock theneedle-less injection device 10 once the device is positioned in thecradle 64 and the cocking and carrying device 60 is closed. Thus, device60 will serve as both a cocking device and case for transporting andstoring the needle-less injection device 10.

In operation, depending on the end use, the user selects an injectiondevice with the appropriate skin pre-tension spring 30, injectiondelivery spring 36, and hammer length. Syringe 18 contains the desiredamount of fluid to be delivered into the skin, muscle or tissue of theanimal or human. The syringe 18 will be inserted into the leading end 14of the inner housing 12, preferably through the use of a bayonet-typeconnector, and mated to a seal that may be a part of the plunger andseal 38.

The outer housing 28 and a cocking and storage mechanism (FIGS. 10 and11) for use with the device 10 will be color coded to inform the user ofthe inner spring power, i.e., the injection power, for that particularinjector device 10.

The variation of the skin pre-tension spring 30, hammer length andinjection delivery spring 36 allows the needle-less injector device 10to be tailored for a particular application. For example, a needle-lessinjector device 10 for use on a child would have one particularcombination of skin pre-tension spring 30, hammer length and injectiondelivery spring 36, while the combination of skin pre-tension spring 30and injection delivery spring 36 for an adult male would likely be adifferent combination. Accordingly, the disclosed invention can theadapted for use on a variety of animals or humans, and for the deliveryof a variety of types injections or depth of delivery of the fluid byvarying the skin pre-tension spring 30 and injection delivery spring 36.

As described above, the user will press the face of the syringe againstthe skin, or fabric, and depress the trigger to give the injection. Theinjector inner housing slides inside the outer housings, which createsan interlock so that the device cannot be operated until the propertension against the skin is established. When the trigger is pressed,the trigger latch will release the hammer and the hammer will move thesyringe seal into the syringe. The main pressure spring will deliverenough pressure to allow the liquid to pierce the skin.

After the injection has taken place, the syringe is removed anddiscarded. With a single dose injector because of the tight seal betweenthe plunger and syringe, the syringe is not reusable. The injector isthen placed into the cocking mechanism and reloaded for the nextinjection.

The syringe and seal assembly can be pre-filled or field filled with theuse of an adapter and a break-away plunger. Thus, syringe 18 can comepre-filled with the desired dose and type of vaccination and insertedinto the injector. Although the above has been described for the use ofa fixed dosage, it should also be appreciated that a multi-dosesyringe/injector is also contemplated by the present invention. The endof the syringe is constructed such that it can be coupled with afield-filling adaptor to download on-site medicaments from a single doseor multi-dose vial or secondary drug-container.

The syringe of the present invention is also constructed and arranged insuch a manner that the drug within the syringe can be lyophilized sothat is can be rehydrated with an adjuvant or saline using the filedfilling adaptor of co-pending U.S. patent application Ser. No.11/453,249, the subject matter of which is herein incorporated byreference. In other words, an adjuvant or saline can be downloaded intothe syringe of the present invention that is filled with a lyophilizedproduct and rehydrated.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

1. A needle-less injector device comprising: an inner housing; an outerhousing supporting the inner housing such that the inner housing isaxially movable within the outer housing between a safe position and afiring position; and a tensioning spring between the inner housing andthe outer housing, the tensioning spring biasing the inner housingtowards the safe position.
 2. The needle-less injector device of claim1, further comprising an adjustable tensioning spring.
 3. Theneedle-less injector device of claim 2, further comprising a threadedplug associated with the adjustable tensioning spring configured topre-tension the adjustable tensioning spring.
 4. The needle-lessinjector device of claim 1, wherein the tensioning spring is selected tocomprise a predetermined tensioning force during assembly of theneedle-less injector device.
 5. The needle-less injector device of claim4, further comprising indicia associated with the outer housing toinform a user of the predetermined tensioning force.
 6. The needle-lessinjector device of claim 5, wherein the indicia on the outer housingcomprises color coding to inform a user of the predetermined tensioningforce.
 7. A method of adjusting a needle-less injector device,comprising the steps of: providing a needle-less injector devicecomprising an inner housing, an outer housing supporting the innerhousing such that the inner housing is axially movable within the outerhousing between a safe position and a firing position and an adjustabletensioning spring between the inner housing and the outer housing; andadjusting the force exerted by the tensioning spring between the innerhousing and the outer housing.
 8. The method of claim 7, wherein theneedle-less injector device further includes a threaded plug configuredto apply pre-tension to the tensioning spring, and wherein the step ofadjusting the tensioning spring comprises applying pre-tension to thetensioning spring with the threaded plug.
 9. The method of claim 7,wherein the step of adjusting the force exerted by the tensioning springincludes selecting and installing a tensioning spring calibrated to apredetermined tensioning force during assembly of the needle-lessinjector device.
 10. The method of claim 9, further comprising codingthe outer housing to inform a user of the predetermined tensioningspring force.
 11. A method for delivering a fluid, comprising the stepsof: providing a needle-less injector device comprising an inner housingadapted for receiving a vial that includes a nozzle for delivering afluid, an outer housing supporting the inner housing such that the innerhousing is axially movable within the outer housing between a safeposition and a firing position and a tensioning spring between the innerhousing and the outer housing; pressing the nozzle against skin bypushing the outer housing towards the skin causing the outer housing tomove towards the nozzle against the force exerted by the tensioningspring until the inner housing is in the firing position, and injectingfluid from the vial through the nozzle.
 12. The method for delivering afluid of claim 11 further comprising: providing an adjustable tensioningspring; and adjusting the force exerted by the tensioning spring betweenthe inner housing and the outer housing.
 13. The method for delivering afluid of claim 12, wherein the needle-less injector device furtherincludes a threaded plug configured to apply pre-tension to thetensioning spring, and wherein the step of adjusting the force exertedby the tensioning spring comprises applying pre-tension to thetensioning spring with the threaded plug.
 14. The method of claim 12,wherein the step of adjusting the force exerted by the tensioning springincludes selecting and installing a tensioning spring calibrated to apredetermined tensioning force during assembly of the needle-lessinjector device.
 15. The method of claim 14, further comprising codingthe outer housing to inform a user of the predetermined tensioningspring force.